A leaked Microsoft product roadmap suggests an early 2013 release date for Office 15 and a fall launch for the next version of Windows Phone, among other tidbits.

The roadmap was discovered by Maarten Visser, CEO of SharePoint and mobility startup called Meetroo, on the Microsoft Partner Network. Visser posted screenshots on Twitter, where they were picked up by ZDNet's Mary Jo Foley. The roadmap was published last December.

Here are the main takeaways:

Office 15 is marked down for an early 2013 launch, alongside SharePoint 15 and Exchange 15. The roadmap shows a summer launch for the Office 15 public beta, which Microsoft has already confirmed.

Some type of Internet Explorer 10 release is marked down for this summer, but it uses a symbol that's inconsistent with the rest of the roadmap. Foley speculates that IE10 will launch alongside the release candidate for Windows 8, though you can already try it out in the Windows 8 Consumer Preview.

The Windows Phone roadmap contains a marker for "Future Investments" this fall. This could refer to Windows Phone 8, if other leaked details prove accurate.

The roadmap shows no release details for Windows 8 beyond the Developer Preview that launched last fall. Since then, Microsoft has launched a public beta, but has yet to announce a release date for the final product.

Foley reports that the roadmap for Silverlight, Microsoft's rich Internet plug-in, shows no releases beyond Silverlight 5, which launched last December. It's unclear whether Microsoft is still committed to the plug-in, which is meant to compete with Adobe Flash.

Microsoft told Foley the roadmap "contains our best estimates, and is, in no way, final or definitive."

Still, I think it's pretty rare for software companies to move up their estimated release dates, so a 2013 launch for Office 15 seems likely at this point. Unless Microsoft is working on a separate tablet version to be released earlier, that could be trouble for the company as it tries to get Windows 8 tablets off the ground later this year.